Variable-speed hydraulic transmission.



- UNITED STATES PATENT OFFICE.

JOHN ROBSON, OF

WESTMINSTER, LONDON, ENGLAND; ASSIGNOR TO THE VARIABLE SPEED GEAR LIMITED, OF LONDON, ENGLAND.

VARIABLE-SPEED HYDRAULIC TRANSMISSION.

. To all whom. it may concern Be it"known that I, JOHN RoBsoN, a subject of the. King of Great Britain, residing at Broadway Court, Westminster, in the county of London England, have invented certain new and useful Improvements in Variable-Speed Hydraulic Transmission, of which the following is a specification.

This invention relates to variable speed hydraulic transmission gears for use with mechanism which it is desired shall be driven at an approximately constant speed.

notwithstanding variations in the speed of the pump unit of the said gear. Such a result is desirable, for example, in the electrio lighting system of railway carriages 'or other vehicles in which a dynamo is able hydraulic transmission gear may be of the kind, for example, wherein each of'the units comprises a cylinder barrel having a number of cylinders which are arranged parallel to the axis of rotation of the barrel and which receive pistons whose rods are pivotally connected thereto and to an inclined plate. The inclined plate of one of the units is carried by a tilting box which can be displaced so that the' stroke of the pistons can be varied, this tilting box being 2 controlled by a governor driven ,by-the pump unit' ora partthat operates it. y

theinvention the inclinedplateof. the motor unit. is the one that isfc arriedby the tilt-. ing box/so that the'stroke of. the motor unit pistons can be varied, andtheinclined plate. of the pump unit is at afixed angle to its shaft, so that the, stroke. of the pump unit pistons is not variable.

In orde that the said inv clearly understood and readily carried into eflectthe same. will be, describedmore fully ithl reference. to theiaccompanying drawingsjin Qwhichzi- 1, I

(Fi s p 1 d 'r f sr..

Specification of Letters Patent.

In he preferred.constructional form 0 may be" in which condition .the iti1ting11 O Qf'i the 05 Patented J line 22, 1915.

Application filed November 14, 1913. Serial N 0. 800,915.

elevation and a plan showing a constructional form of the invention. Fig. 3 is a view similar to Fig. 2 showing the invention employed for train lighting, and Figs. 4, 5 and 6 are views of details hereinafter described.

A is the pump unit, B the motor unit and C the shaft driven by the latter.

D represents the control shaft that actuates the tilting box of the motor unit B, and E represents the governor that controls the inclination of the said tilting box.

The governor E is shown as being of the centrifugal type and is driven in any suit able manner from the shaft of the pump unit A, for example by means of spur gearing as shown. The usual sliding sleeve e of the governor is connected to a forked or other suitably formed lever e (Fig. 4) which is pivotally attached to one end of a sliding rod E. The other end of this rod is in the example shownformed with rack teeth that gear with a pinion d on the control shaft D of the tilting box. By these means the position of the tilting box 1s directly influenced by the speed at which the governor is driven.

When the pump is being driven -at its maximum speed the tilting box of the m0- tor unit-B will be at the same angle to its shaft as the inclined plate of the pump unit A, and the shafts of the pump and motor units A, B will then be running at the same speed. If the speed of the pump is reduced, the governor E will operate the tilting box so as to-bring the latter to an angle nearer the neutral position e. a position at right angles to its shaft. The

stroke of the motor unit pistons will then be less than, the stroke-of thepumpfunit pistons. and consequently. the shaft driven by the motor unitB- will rotate at a higher speed than the shaftof the pump unit A. Inthis manner thespeed of the motor unit. shaft can be keptconstant for any speedofthe pump unit shaft.

In order to lessen the; internal lfliiid sistance of the pump and InOiZOITfllIlitS when; I the pump unit A.-is starting from -rest g motor unitB is in itszeropos tio fithea valve, plate F (E g. ,6.) may be; -provided. 5 g

stem carries a plate f having two projections arranged at a suitable distance apart, one or the other of these pro ect1ons belngengaged by a pin e 'on'thc sliding rod E I ters Patent of the United States 1s::

5 during the movement of the latter. The bypass valve is opened by the said sliding rod during the final movement thereof after the speed of the pump unit has fallen below a predetermined limit and is closed when the LO speed of the pump unit exceeds this limit.

3y means of this valve the liquid is allowed to flow through the by-pass between the two ports in the valve plate for a short period immediately before the stopping and aftcrthe starting of the pump unit. During this period after the starting of the-pump unit the tilting box is moved by the action of the governor E until it reachesa position corresponding to the minimum speed of the pump unit at which it is desired to drive the shaft C11 The starting resistance in the apparatus is thereby considerably lessened,

-. owing to the pistons in the motor unit B having an appreciable stroke before the ifli l'oad is applied. v y

The governor E may be placed in any convenient position either parallel or at right angles to the longitudinal axis of the pump and motorunits, and may be of any suitable ltype. The control shaft D operating the Y tilting box of the motor unit B may if desired be operated directly from thesliding rod E or from the lever e' 'and the shafts of the pump and motor units maybe arlranged with their axes either in alinement with or at any desired angle to each other.

The improvements are as aforesaid particularly intended for use in an. electric lighting system for trains or other vehicles.

"40 Fi g. 3 shows the improvements employed inthis connection, the pump unit A' being driven by a belt from a pulley A onfthe vehicleaxle. The shaft C that is operated by the motor unit B drives a dynamo; F

fi employed for lighting the vehicle. The nee essary switch apparatus for placing into a "d out of operation the storage batteries usual l iz, provided. can be worked simultaneously withip.

,the opening and closing-of the by-pass valve by means of the sliding rod E.

Although there has been described as the preferred constructional form of the invention an arrangement in which the inclined.

plate of the motor unit is adjustable and i that of the pump unit is at a fixed angle with respect to its shaft, the inclined plate of the pump unit may be made adjustable,

that of the motor unit being then at a fixed In this case the inclined plate of angle. the pump unit would, when the vehicle is running at full speed be approximately midway between its zero and maximum positions, the inclined plate of-the motor unit being parallel to that of: the pump unit.

M When the speed of the vehicle is reduced, the

clined plate of the pump unit toward its maximum position.

lVhat I claim'and desire to secure by Letl. In a variable speed hydraulic transmission gear, the combination with the pump 1 unit and the motor unit, of means operated by the pump unit for automatically maintaining the speed of the motor unit constant notwithstanding variations in the speed of the pump unit.

2. In a variable speed hydraulic transmission gear, the combination with the pump unit and the motor unit, of means under the influence of the speed of the pump unit for automatically maintaining. the speed of the motor unit constant notwithstanding variations in the speed of the pump unit.

3. In a variable speed hydraulic transmission gear, the combination with the pump unit and the motor unit, of means under the influence of thespeed of the pump unit for automatically varying the relative piston strokes of the said units during variations in the speed of the pump unit. f

4. In a variable speed hydraulic transmission gear, the combination with'the pump unit and the motor unit, of means under the influence'of the speed of the pump unit for automatically varying the piston stroke of the motor unit during variations in the speed of the pump unit.

5. In a variable speed hydraulic transmission gear the combination with the pump unit and the motor unit, of a governor driven from the pumpunit, a control member for the motor unit, and means for ac tuating said member from the-governor dur ing the movements .of the latter under the influence of variations in the speed of the pump unit. u

,6. In a variable speed hydraulic transmis,- sion gear. the combination with the pump unit and the motor unit, of means for automatically maintaining the speed of the motor unit constant notwithstanding varia- J tions in the speed of the pump unitQfand means for short circuiting the fluid pumped by the-pump unit, for any desired period "afterthe starting of the pump unit.

7. In a variable speed hydraulic transmission gear, the'combination with the pump unit and the motor unit. of means for automatically maintaining thespeed of the-mo tor unit constant notwithstanding variations in the speed of the pump unit and means for short circuiting the fluid pump d b I the smpping and flflerthe. ar g of the pump unit, for any desired period before pump unit. y

8. In a variable speed hydraulic transmission gear the combination with the pump iinit and the motor unit, of means for automatically maintaining the speed of the mo- I tor unit constant notwithstanding variations in the speed. of the pump unit,- a by-pass valve for short circuiting the fluid pumped umt.

sion gear, the combination with the pump 10 9. In a variable speed hy'draulic transmisunit' and the motor unit, of a-controlmember for'the motor unit, a governorv driven by the pum unit, a device foractuating said member rom the governor during the movements ofthe atter under the;

.variations in the speed of the pump unit, 15 a a by-pass valve for short circuiting the fluid pumped by the pump unit, aplate on the stem of said valve, two projections arranged on said plate at a suitable distance apart and a pin, on the aforesaid device, for co- 20- operating with one or other of said pro]ections' to open and'close the bv-pass valve.-

In testimony whereof'I aflix my signature. in presence of two witnesses. v Q JNO.-ROBSON.- Witnesses: I j

,TLSELBY; WARDLE, Tnos. F. HARGREAVES. 

